The present invention is related to oil and gas well blowout prevention. More particularly, the invention is related to actuating relief valves in conjunction with the actuation of blowout preventers.
Oil and gas well blowout preventers are constructed to close about a pipe in a well in order to block the upward flow of fluids from the well in the open space between the casing and drill pipe hole during drilling and completion operations.
Blowout preventers are well known in the art. Examples of blowout preventers and blowout preventer components are contained in the following U.S. Pat. Nos. 2,188,141; 3,589,667; 4,098,341; 4,098,516; and 4,192,379.
It is also known in the art to insert a pressure relief line beneath the blowout preventer in the casing to allow some of the fluids trapped in the space between the drill pipe and the casing when the blowout preventer is actuated to escape to the atmosphere or to some reservoir. Such a pressure relief line has a valve therein which may be opened and closed to selectively release fluids through the pressure relief line. The valve on a pressure line is commonly operated by hydraulic lines which actuate the valve when pressure on the blowout preventer is sufficiently high. The pressure relief line must be opened rapidly or the blowout preventer may explode, endangering the lives of the personnel operating the well and destroying equipment adjacent thereto. If the hydraulic system operating the valve on the pressure relief line should fail for any means, such an explosion can occur.